Atlant’s Column: The secret of the rose

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Welcome to the section on Micronaut.ch which explores, analyzes and explains fascinating microscopical structures.

Rose Petal Surface IRoses look lovely. But their beauty holds a secret. If you look closely, you discover something on the flowers even botanists cannot explain.

If a man gives roses to a woman, it means: I love you. Already the ancient Greeks were so charmed by the shape of the rose blossom that they dedicated it to Aphrodite, the goddess of love. However, the petals of some rose species possess a characteristic that more resembles an animal than a love goddess. Their outside is covered with a fur of fine hairs. They are between 0.2 and 0.5 millimetres long and grow away from the stalk in the direction of the opening flower. With a thickness of 7 microns they are about ten times thinner than a human head hair.

Rose Petal Surface II

With the naked eye, they are not visible and if you run your fingertips over the petals, you will hardly have the feeling of stroking a fur. But what are hairs doing on a rose flower anyway? Not even biologists know the answer to this question.

Plant Hairs are One of the Great Mysteries in Botany

In fact, the hair-growth of plants is one of the great mysteries in botany. There are only a few cases where its function has been clearly determined. For instance, hairs on leaves of desert plants often serve to reduce water loss. They cover the leaf surface like a windstopper fleece and thus prevent the dry air from dehydrating the leaf cells. In carnivorous pitcher plants, on the other hand, the hairs form a slippery surface on which potential prey easily loses its grip and falls into the pitcher, where it is digested.

Rose Petal Surface I

Hairs can also have a transporting function. Cottonseeds, for example, are surrounded by cotton. These very long and light hairs are designed for air transport. When the wind blows into the popped capsules, it carries away the cotton together with its enclosed fright. Like this, the cotton can colonise new and distant areas.

Why the petals of roses have hairs, can currently only be guessed. It could be that they protect the unopened flower against external influences. This can be rain, wind, insects, or the touch of neighbouring roses and leaves. Rose petals are very vulnerable and wilt quickly if they have a scratch. The rose wants to avoid this at all costs. Because, if the flower is damaged before it opens, it could decrease its chance for successful pollination. Thus, the hairs on the outside of the petals could serve as a reinsurance for love.


More information on hair-growth of plants.

 

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